Cryptographic apparatus



Dec, 13, 1938, w. F. FRIEDMAN CRYPTOGRAPHIC APPARATUS Filed Aug. 4, 1957 5 Sheets-Sheet l Nun wk QT m\ @OQQOGOOO DQ096606 Dec. 13, 1938. w. F. FRIEDMAN CRYPTOGRAPHIC APPARATUS Filed Aug. 4, 1937 3 Sheets-Sheet 3 I llllllillllllllbllll MLL/AM FRIED/14 Patented Dec. 13, 1938 UNITED STATES ATE OFiCE (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to cryptographic appa- I ratus for automatically enciphering and deciphering messages.

An object of the invention is the provision of a cryptograph with a keyboard for high-speed manual operation, a bank of indicating devices or electro-magnets for noting or recording the cipher symbols of the messages as the latter are being enciphered, and for noting or recording the plain-text letters as the messages are being deciphered; and certain ciphering mechanisms interposed between the keyboard and thebank of indicating devices or electro-magnets for constantly changing the relationship between the message characters and the cipher symbols. The

invention is primarily concerned only with the ciphering mechanism referred to above, which is of simple design but nevertheless yields cryptograms of great security. This ciphering mechanism em ploys means which are novel in the cryptographic art in that it involves operation along a time axis, and the exact cryptographic results are dependent upon a time factor which is constantly changing in an irregular manner.

The invention is described in connection with the accompanying drawings, in which:

Fig. 1 is a diagrammatic representation of the parts of the mechanism together with certain circuit arrangements;

Fig. 2 is a diagrammatic representation of 5 means for imparting uniquenessto messages even when the latter are enciphered by the same keying sequence;

Fig. 3 is a diagrammatic representation of the electrical circuits applicable to the system shown in Fig. 2; and

Fig. 4 shows an alternative scheme for one of the basic elements of the mechanism shown in Fig. 1. I Referring to Fig. 1, the principal elements consist of -a keyboard I, a bank of indicating devices 2, a rotating cipher commutator hereinafter calleda rotor 3, a distributor 4, a camwheel mechanism 5 for producing a cipher key, a permutation-translation mechanism hereinafter called a translator 6, and a switchboard 1.

According to the present invention, means are provided whereby the individual alphabets of a 7 set of twenty-six or more mixed cipher alphabets are caused to present themselves for ciphering purposes in a fixed sequence and this sequence is regularly repeated. When a key on the keyboard is depressed only one of these cipher a1- phabets, however, is selected during one complete presentation of the sequence of alphabets and the cipher resultant obtained depends upon 5 the cipher alphabet that has beenselected. This selection is varied according to a very long cipher key.

Broadly speaking, the foregoing cryptographic operation is accomplished inpracticing the in- 10 vention in the following manner:--

The rotor 3 serves as switching means for changing the whole set of twenty-six connections between the keyboard I and the bank of indicating devices 2. The rotor is caused to rotate with 15 a constant angular velocity by the motor 93, and the time required for the rotor to make one complete revolution will hereinafter be referred to as the operating cycle. Assuming a system employing twenty-six elements (to correspond with the 20 twenty-six letters of the English alphabet) rotor 3, in making a complete revolution will pass through twenty-six angular positions, each consuming & of the time required for the rotor to complete one operating cycle. The operating 25 cycle may therefore be regarded as being subdivided into twenty-six equal time-intervals during which a letter may be enciphered by the cryptograph. To each of these time-intervals or angular positions of the rotor, there corresponds a cipher alphabet, that is, a set of connections between the keyboard and the bank of indicating. devices. Coordinated with the rotor is the distributor 4, whose brush arm l6 causes brush 13 35 to sweep over the twenty-six equal segments of the face of the distributor synchronously with the rotation of the rotor. The distributor coop-- crates with the keying mechanism to determine which of the cipher alphabets will be selected. 40

that is, which of the twenty-six angular positions of the rotor, or which of the twenty-six time-intervals, will be the one selected during a specific operating cycle for encipherlng (or deciphering) a letter. This selection in each case 4 varies with the successive operating cycles according to a cipher key which is produced by the cam-wheel cipher-key mechanism 5. Each different one of the twenty-six time-intervals will yield a difierent resultant for the same letter; 50 therefore there are twenty-six difl'erent resultants possible for each letter. Within the operating cycle, when a key of the keyboard is depressed, the letter corresponding to this key is enciphered (or decipher-ed) by that one of the 55 cipher alphabets which was selected in the aforesaid manner. Arrangements are made for locking up the keyboard so that when a key is depressed not only will the associated keyboard contact be closed but also it will remain closed for one whole operating cycle and no other key can be depressed during that same cycle. Thus, keyboard operation may be regarded as being rhythmic in character and may be performed with a cadence similar to that in teletype operation. The operation of the keyboard results in the action of the responsive indicating devices 2, which may print the characters produced by the ciphering operation in a rhythmic manner. But it is obvious that this cadence does not have to be reproduced identically by the operator who is to decipher messages for the cadence is not at all an essential part of the functioning of the apparatus. In fact, if a clutch mechanism were provided whereby the rotor and the distributor would only be started consequent upon the depression of any key of the keyboard, and would be stopped automatically at the end of the operating cycle, then for each depression of the key the rotor and the distributor brush arm would start, would make one complete revolution, the letter would be enciphered (or deciphered) and upon completion of the revolution both the rotor and the distributor brush arm would stop. Thus, no cadence in keyboard operation would be required, and operating speed would only be limited by practical considerations.

The foregoing apparatus and its operation will now be described in detail.

The keyboard I, comprising 26 characters equivalent to the letters of the alphabet, has a corresponding number of contacts of which only two are shown as at 10 and 11, corresponding to the letters E and Q, respectively. The bank of indicating devices 2 may take the form of glow lamps which are illuminated when current passes through them but a preferred embodiment is to have the indicating devices take the form of electro-magnets or solenoids which operate the keys of a recording typewriter, so that a printed record of the enciphered or deciphered message may be made.

The rotor 3 is a cipher-commutator wheel of form now well known in the cryptographic art. It is mounted on a rotatable shaft I2. Pressing against rotor 3 are two stators, a left-hand stator I3 and a right-hand stator I4, each provided with a ring of 26 ball-bearing and spring contacts insulated from one another and exerting a slight pressure against the face of rotor 3. A motor 33, drawing power from source 34, drives the shaft l2 and thus the rotor 3 at a constant speed between the stator' I3 and I4. The rotor is made of Bakelite or similar insulating material and consists of two faces, a lefthand face and a right-hand face each face hearing a ring of 26 contact surfaces A, B, C, Z, equidistantly spaced from one another circumferentially on the outer face. Insulated conductors passing through the rotor connect the 26 contact surfaces of the left face to those of the right face, in-a manner which is reciprocal in pairs. That is, if A on the left face is connected to X on the right face, then X on the left face is connr ated to A on the right face. Thus, with 13 paired contacts reciprocity in the encipheringdeciphering relationship'is obtained without spetially on the face of the distributor.

from one another and distributed circumferen- A brush arm l6, on the same shaft l2 as the rotor 3, sweeps over the face of the distributor 4 at a constant rate of speed synchronous with that 5 of the rotor 3. The rotor 3 and brush arm I6 are keyed to the shaft I2 so that these two elements are always in a fixed angular relationship with respect to the shaft I2 and cannot be angularly displaced relative to each other, due to slippage on the shaft. Arrangements may be made, however, to change the relative angular positions of the rotor and the brush arm if desired. -Brush arm I6 terminates in a brush 13 which sweeps over distributor segments I5 and establishes momentary contact with each of the latter successively. Distributor segments I5 are connected to the right-hand set of terminals I2 of switchboard 'I by a set of conductors II, of which only a few are shown.

The cam-wheel cipher-key mechanism 5 provides a long cipher key for cryptographic purposes. It consists of five or a multiple of five cam-bearing wheels 2|, 22, 23, 24, 25 of different diameters. The periphery of each wheel is divided up into equal segments to which projecting lugs serving 'to act as cams may be attached or into which. cams may be inserted; the numbers of segments on the different wheels are prefably prime to one another. For example, wheel 2| may have 100 segments, wheel 22 may have 99, wheel 23 may have 97, wheel 24 may have 91, and wheel 25 may have 89. Fixed to these wheels are ratchets 26, 21, 28, 23, 30. The number of teeth in eachratchet 26 to 30 corresponds with the number of segments in the cam-bearing wheel with which the ratchet is associated. Pawls 3|, 32, 33, 34, 35 on a rocker arm 36, which is operated by magnets 31, 38, drive the cam-bearing wheels in a stepwise manner, under control of a universal bar key-board contact 33 through power source 40. Each time a key is depressed rocker arm 36 and the pawls 3| to 35 serve to step wheels 2| to 25 forward one interval. The cams on the peripheries of the cam-bearing wheels 2| to 25 control contact levers 4|, 42, 43, 44, 45 and the latter operate contacts associated therewith, I4I, I42, I43, I44, and I45. It will be understood that the segments 'on the periphery of each wheel 2| to 25 are smooth surfaces except where a cam is inserted in or aflixed to the segment and each wheel may have a cam inserted in any number of the slotted segments. Contact levers 4| to 45 are therefore raised and their associated contacts |4| to I45 are closed only when cams are presented to them by the progressive movement of the wheels 2| to 25. Furthermore these contact levers 4| to 45 will be operated in permutative groupings so that all 32 possible Baudot-code combinations may be set up by the contacts I to I45, for keying purposes. Contacts I to I45 are connected to conductors 46 to 56 and control magnets 5| to 55, the function of which will be described presently. Now since the cam-bearing wheels 2| to 25 are of different diameters and they all step forward one step for each depression of a key on the key-board I, if these wheels are initially aligned at a bench mark so as to correspond to a cipher key, this initial alignment will recur only after 100 99 97 91x89 or 7,777,469,700 letters have been enciphered (or deciphered) Thus a cipher key of great length is made available for cryptographic purposes.

The translator 6 is an instrumentality well 75 known in the art of printing telegraphy. It consists of a set of five translator bars 6| to 85 which are normally held in position by the retractile springs 56 to 68. The translator bars are slotted according to the requirements of the Baudot or 5-unit printing telegraph code, so that 32 different alignments of slots may be presented to a set of 32 stunt bars labeled 66. Only one stunt bar can drop into a specific alignment of slots and when this occurs a contact associated with the selected stunt bar is closed. Several of .these contacts are shown at 61, it being obvious that there are 32 such contacts in all. Thesecontacts 61 are connected to conductors 68 which lead to the set of 32 terminals 88 of switchboard I.

It will now become clear that the cam-wheel cipher-key mechanism 5 serves merely to select one out of 32 circuits leading to the terminals 88 of switchboard 1 and that this selection, being quite variable and depending upon the successive permutations set up by the cam-wheel mechanism 5, thus produces a long, variable sequence of keying circuits corresponding to keying characters and hereinafter referred to as the keying sequence.

The 32 terminals 89 of switchboard I are connected to a corresponding number of flexible conductors I0, and the latter terminate in jacks, which may be inserted into plugs II connected to terminals I2 on the other side of switch I. There are but 26 such plugs II and each of them has apair of holes for receiving jacks, but only six of these double-hole plugs will have both holes occupied by jacks. By this arrangement the 32 possible resultant keying circuits set up by translator 6 are reduced to 26, of which six will be double-effects, that is, in six cases the same keying character may be brought about by two diflerent Baudot permutations setup by the translator 6. Which six keying circuits these will be depends upon the way in which the flexible conductors I are connected to plugs II at any given time. It will be seen later that no ambiguity is occasioned by the presence of a keying circuit which is of the double-client type.

Still referring to Fig. 1, the electrical circuit for cryptographic functioning will now be described. It will be seen that the circuit from power source I8 to the keyboard I must pass through contact I9, which is controlled by main relay 8. Hence, depression of any key of keyboard during the time contact I9 remains open will produce no efiect since no power is being delivered to the key board I and hence no circuit to the bank of indicating devices 2 is established.

Let us see now upon what circumstance closure of contact I9 depends; in other words, let us see when main relay 8 will be energized. Let us consider a specific operating cycle a: in the long sequence of operating cycles 11.. During this operattor 4. Which of the 26 segments I of distributor 4 will be alive, that is, connected to power source 20 during operating cycle 2: depends upon 8, conductor I6, armature I1 and back contact 18 of relay 9, conductor I9, brush arm I6 and brush I3 of distributor 4; the brush then being on segment I8 the current continues through.

segment 14, conductor 80, to one of the contacts I2 of switchboard I, and thence' through the switchboard along one of the flexible conductors I8 to one of the contacts 69 on the other side of the switchboard, thence along one of the conductors 68 to that one of the contacts 61 which is closed by the selected stunt bar 66 of translator 6,- finally along common return conductor 8|, back to power source 20. Relay 8 is energized at the instant that brush I3 is passing over live seg- A circuit is completed as. follows: power source 28, conductor I5, main relay ment M, and since rotor 3 revolves synchronously with brush arm I6, the angular position of rotor 3 with respect to its stators I3 and I4 corresponds to the angular position of brush arm I 8 at that instant. The cipher resultant produced by depressing a key on key-board I will be determined by the angular position of rotor 3. The reason for this is that since rotor 3 has 26 ciphering positions each yielding a completely difierent set of.

c pher. resultants for the 26 character keys or keyboard I, the specific cipher resultant for a. specific keyboard character enciphered within a specific operating cycle at. depends upon the specific segment ofv distributor 4 which is alive during that cycle The circuit through the keyboard I. the rotor 3 and the bank of indicating devices 2 will now be described. When a key I8 corresponding to the letter E" is depressed during operating cycle 1'. nothing happens until brush I3 reaches segment 14 of distributor 4, for the keyboard remains dead until that moment. The instant that re-- lay 8 is energized, current is delivered from power source I8 through closed contact I 9 and armature 82 of relay 8, along conductor 83 to the contacts of keyboard I. Since contact I8 is closed, the current continues along conductor 84 to a contact on stator I3, thence through the rotor 3, which is at that instant in an angular position corresponding to that of brush arm IE, to' a contact 85 on right stator I4, thence along conductor 81' to indicating device or solenoid 88, which corresponds (in this figure) to letter Q" thence along conductor 80 through slow acting relay 9, finally along conductor 8| back to power source I8. Solenoid 88 is actuated (or if lamps are used a lamp is lighted) to indicate the cipher resultant Q for plain-text letter E".

When slow-acting relay 8 is energized the circuit for main relay 8 is broken at 18 when armature 'I1 is withdrawn. A mechanically controlled trip 92 engages lever I1 and. holds it away from contact I8 until the universal bar on keyboard I returns to normal when the key is released, whereupon lever 11 is allowed to fall back and close I8. The purpose of this arrangement is to insure that not more than one letter will be indicated'or printed per operating cycle, that is, per depression of a key on the keyboard.

When the universal bar on the keyboard I reaches the end of its downward stroke it closes contact 39, which controls the circuit to magnets 31 and 38. .Rocker arm 36 is operated, causing pawls 3| to 35 to engage ratchets 25 to 30 and advancing cam-bearing wheels 2| to 25 one step forward to the next position, setting up a new Baudot permutation of contact-levers 4| to 45, assocated contacts I to I45, and magnets 5| to 55. A new keying character is thus established by translater 6 and the system is now ready for the next operating cycle. Even if the same key is depressed on the keyboard the equivalent produced at the bank of indicating devices will be diiferent, unless the keying character happens accidentally to be the same as before. Continued depression of the same key will produce a varying sequence of equivalents corresponding in length with the length of the keying sequence produced by the cam-wheel mechanism 5. This latter sequence is of great length, as has already been explained, being the resultant of the interaction of five wheels of different diameters with different numbers of teeth, these numbers being prime to one another.

Since the connections within the rotor 3 are reciprocal in pairs, as explained, the decipherment of a message takes place by resetting the wheels of cam-:wheel mechanism 5 to the initial key position, and operating the keyboard I to correspond with the cipher letters, whereupon the plain-text equivalents will be produced at the bank of indicating devices 2.

The mechanism shown in Fig. 1 and described in the foregoing terms is such, however, that if several messages are enciphered by the same keying sequence they will be in the same series of cipher alphabets, and in this case there exists a possibility of a solution by cryptanalytic procedure. To explain what is meantby these statements it is necessary to call attention to the fact that the cipher commutator 3 provides a set of 26 cipher alphabets and that basically the cryptographic principle of the system as described is one in which the individual alphabets of this set of 26 cipher alphabets are brought into play in an order determined by the keying sequence set up by the cam-wheels. For example, suppose we consider this keying sequence to be such that for a given key as set up on the cam-wheels the first 20 alphabets to be brought into play are alphabet numbers It, 4, I9, 26, I5, 3, ll, 2|, l2, 5,1, ll, 22, I, I3, ll, 28,2, ll, 24. Now if several messages start with the same initial cam-wheel setting. the successive letters of all these messages will be in the same sequence of cipher alphabets, and therefore the several messages may be superimposed, yielding columns of letters which are monoalpha betic in composition. Or, even if the messages .do not start at exactly the same point in the keying sequence, but portions of these messages overlap one another with respect to the keying sequence, then the overlapping portions which are in the same alphabets, may be superimposed.- For exam-'- ple, using the same sequence of alphabet numbers mentioned above, suppose a first message begins with alphabet number li, a second message, with alphabet 4, a third one, with alphabet l3, and so on, it is merely a to shift the second message one letter to the right of the first, shift the third message one letter to the right of the second,

and then all three messages will be properly superimposed with respect to the keying sequence; the letters in columns are now in the same cipher alphabets, and the messages are susceptible of solution by monoalphabetic principles. The proper points for superimposition can be ascertained even without a knowledge of the particular key settings for these three messages, from a detailed study of the repetitions between messages. It is necessary. therefore, in order to circumvent this possibility of superimposing messages or parts thereof so that they will be in the same keying sequence, to impart a cryptographic uniqueness to the messages so as to destroy, mask, or suppress repetitions brought about by the chance encipherment of identical words by identical sequences of alphabets.

Mechanism for accomplishing this is shown in Fig. 2. Here the shaft |2| carries several cipher commutators or rotors, 3a, 3b, 3c, 3d, and 32. These rotors are separated from one another by stators I22, I23, I24, I25, each carrying rings of contacts on both faces, to provide for continuity of circuit from one rotor into the next. The contacts in these stators, as are those in stators l3 and I4, already described, are ball-bearing spring contacts and they press against the rotors so as to hold each rotor in place, and keep it from rotating on the shaft l2, except when rotatory motion is imparted to it by means to be described. The periphery of each rotor 3a to 3e bears a collar 2|! in which 26 gear teeth have been cut so as to engage with gear wheels 2|3 and 2 M which are mounted on shaft l2, the latter now corresponding to shaft |2 of Fig. 1. Gear wheels 2|! and 2 can be independently slid sidewise along the shaft I2 and keyed into position on the shaft, by means not shown, so as to engage the toothed collars of any two of the live rotors 3a to is, at the will of the operator. Gear wheels 2|3 and 2" have 26 teeth and their pitch is the same as those on the collars of rotors 3a and 3e, so that the motion imparted to a rotor by wheel 2|3 or wheel 2" is a 1:1 drive. The shaft I2 is rotated by motor 93, as in Fig. 1; the distributor 4 of Fig. 2 is the distributor similarly numbered in Fig. 1, with the brush arm l6 and brush I3. Thusjinstead of driving one rotor 3, as in Fig. 1, the motor 93 and shaft I! may drive any two of the five diflerent rotors 3a to 30. The function of the distributor 4 and brush am I6, is now the same as described in connection with Fig. 1, but the rotor that will be associated with these elements is now susceptible of variability.

The rotors 3a to 3e are to be set to a key, by aligning the letters on their peripheries at a bench mark. Since there are 26 individual rotatory positions of each rotor on the shaft, there are 26 diiferent initial settings of these rotors, each such setting providing a different set of 26 paths for the passage of electric currents from the keyboard I to the bank of electro-magnets 2. The circuits from the keyboard I through the set of rotors 3a-e to the bank of solenoids 2 are shown diagrammatically in Fig. 3. In this figure stators i3 and I4, and rotors Ia to Is correspond to the similarly designated stators and rotors of Fig. 2, The internal wirings of rotors 3a, 3b, 3c, and 3d are not reciprocal in pairs, as isthe case with the single rotor I of Fig. 1, but are all random connections. The rotor Se is, however, different in its construction from the other rotors,-

in that it has a ring of contacts on only one face and these contacts are interconnected in pairs. Thus rotor 3e serves as a means for reversing a current coming into the set of rotors from a con tact in stator l3, passing through rotors 3a, 3b, 3c, 3d, and sending it back through rotors M, Sc, 3b, 3a to another contact in stator l3. Stator |4 now serves no electrical function but merely as a mechanical bearing against which rotor 3e presses. Relay 8, contact I 9, armature 82, and battery I8 correspond to similarly designated elemerits of Fig. 1. The keys of the keyboard I now serve a double function instead of a single function as in Fig. 1. Each key operates a lever which opens one contact and closes another. I For instance, when the E key is depressed contact lever I is withdrawn from contact III and makes contact at I I2. When relay 8 is energized a cur rent flows from battery I8, along conductor 83, contact II2, lever ID, conductor 85 to a contact I I in stator I3, thence through the rotors and back to another contact I I6 in stator I3 thence along conductor 84, lever I I, contact I I3, solenoid Q, back to battery I8. Solenoid Q is actuated and the cipher resultant of E is Q. In deciphering, assuming that the rotors are in the identical position they were in when enciphering (the cipher key being the same), on'depressing the Q key of the keyboard it will be seen that the following reciprocal deciphering circuit is established: Battery I8, conductor 83, contact H4, lever I I, conductor 84, contact H6 in stator I3, through and back through the rotors to contact 'I I5, conductor 85, lever Ill, contact III, solenoid E, back to battery. Thus, the plain-text resultant of Q is E. In this manner a reciprocal enciphering-deciphering relationship is readily established.

We will now consider the cryptographic operation of the system after the introduction of the foregoing features. The key for a message will now consist of the following elements:

(1) The composition of the cam wheels, (that is, the positions of the cams on the wheels) and their initial setting or alignment at a bench mark; the connections at switchboard I.

(2) The composition of the rotors, that is their internal wiring; the relative order of rotors 3a, 3b, 3c and 3d on the shaft, and the initial setting or alignment of all the rotors at a bench mark.

(3) The rotors which are selected for engagement with gear wheels 2 I3 and 2 I4.

It becomes obvious that even if two messages are identical, letter for letter, even if they begin at exactly the same point in the keying sequence produced by the cam wheel assembly, and even if gear wheel 2I3 is engaged with the same rotor, so long as the setting of the rotors 3a to 3e on shaft I2I is different by at least one letter for these two messages, or so long as either of gear wheels 2I3 and 2 I4 is set to drive different rotors, the cipher texts will be different and externally there will be no sign of the internal identity of the two texts. Furthermore, there is nothing to prevent there being three gear wheels similar to 2I3 instead of only two, as shown in Fig. 2, in

which case three of the five rotors can be driven.

And, of course, if there were say rotors it would be possible to .have any number up to 9 of such driving gear wheels, thus affording a very wide range for keying purposes. In other words, as now fully developed, the system provides for a multiplicity of keys, such that a uniqueness may be imparted to messages even in the same cam wheel keying sequence, with a correspondingly high degree of cryptographic security.

The translator mechanism IS in Fig. 1 may be replaced by a system of interconnected contactlevers 96, and associated paired contacts shown schematically in Fig. 4. In the latter figure, the contact levers 4| to 4'5 and the magnets 5| to 55 are homologous with similarly designated contact levers and magnets of Fig. 1 and serve the same function; the bars 6| to 55 of Fig. 4 are homologous with similarly designated bars of Fig. 1 and serve an equivalent function, viz., to set up, by permuative arrangements of actuated and nonactuated bars, permutative arrangements of contact-levers operating switches to establish one of 32 difierent circuits to the terminals of switchboard I. It will be seen that permutative arrangements of the contact-levers as to the left or right positions will result in selecting one of 32 paths for a current flowing from power source 20 to the switchboard I. The magnets 5| to 55 and their associated bars 6| to 65 maybe replaced by multiple-contact relays well known in the art.

Changes, modifications and equivalent arrangements are contemplated within the scope velocity through all said positions, each complete revolution of said rotor mechanism consti-.

tuting a ciphering cycle and each said ciphering cycle corresponding to the time duringwhich a key of the keyboard is depressed; and means for selecting one of said potential ciphering positions to become the operative ciphering position within a ciphering cycle.

2. In a cryptograph, a keyboard comprising a set of character elements, and a corresponding set of signaling elements in operative electrical connection; a cipher rotor mechanism for varying the connections between the character elements and the signaling elements, said rotor mechanism having a multiplicity of potential ciphering positions and being driven sequentially and repetitively at a uniform angular velocity through all said positions, each complete revolution of said rotor mechanism constituting a ciphering cycle and each said ciphering cycle corresponding to the time during which a key of the keyboard is depressed; means for selecting one of said potential ciphering positions to become the operating ciphering position within a ciphering cycle; and means for varying the selection with successive ciphering cycles, the latter corresponding to successive depressions of the keys of the keyboard.

3. In a cryptograph, a. keyboard comprising a. set of character elements and corresponding contacts electrically associated therewith; an indicating mechanism comprising a set of signaling elements corresponding in number with the number of character elements and in circuit relation therewith; means for establishing and varying the electrical connections between the character elements and the signaling elements, said means including a cipher rotor having therein a set of insulated conductors, said rotor being capable of assuming a rnultiplicity'of potential ciphering positions; means for driving said rotor sequentially and repetitively at a uniform angular velocity through all said ciphering positions; each complete revolution of said rotorconstituting a ciphering cycle and each said ciphering cycle corresponding to the time a key of the keyboard is depressed; means for selecting one of said potential ciphering positions to become the operative ciphering position within a ciphering cycle, said means comprising a distributor mechanism and a brush timed to revolve about the face of said distributor synchronously with said rotor; a circuit including a relay, which when actuated connects the keyboard for operation, said relay being controlled through said circuit in which is included the brush of said distributor mechanism; a translator, and contacts closed by said translator; a set of cam wheels for controlling said translator; and means for angularly displacing the respective cam wheels of said set with successive depressions of the keys of the keyboard.

4. In a cryptograph, a keyboard comprising a set of character elements; an indicating mechanism comprising a set oi signaling elements, both sets of elements being in circuit relation; a cipher rotor for establishing a multiplicity of connections between the character elements and the signaling elements; means for driving said rotor sequentially and repetitively through the entire series of such connections, the time required for the rotor to pass through said series of connections corresponding to an operating cycle; a distributor the face of which is divided up into insulated segments corresponding in number with the number of character elements, and having a brush sweeping said segments synchronously with the rotor; a cam wheel mechanism for establishing a cipher key; a translator mechanism for combining the eiiects of said cam wheel mechanism; a switchboard for reducing the said eflects to-a number corresponding with the number of character elements; a source of potential; and a relay controlled by the cam wheel mechanism through the intermediacy of said translator mechanism and distributor for the purpose of connecting the keyboard to said source at a selected instant within the operating cycle.

5. In a cryptograph, a keyboard comprising character elements, an indicating mechanism comprising signaling elements, and a cipher rotor for establishing and automatically, rhythmically, and sequentially varying the connections between the character eleme'its and the signaling elements; means for selecting one of a set of said connections during the time a key of the keyboard is depressed; and means for varying the selection with successive depressions oi! the keys or the keyboard.

6.Inacryptograph,acam-wheel mechanism for establishing a cipher key sequence consisting of permutations of a plural-unit code; and means tor-translating the permutations set .up in said code'by said cam-wheel mechanism into a limited number or single-unit keying characters.

I. In a cryptograph, a cam-wheel mechanism for establishing a cipher key sequence consisting of permutations of a plural-unit code; means 101' translating the permutations set up in said code by said cam-wheel mechanism into a limited number of single-unit keying characters; and a switchboard for reducing said keying characters to a smaller number.

8. In a cryptograph which employs a translator assembly having permutation bars and stunt bars in operative electrical connection; means for producing a relatively long cipher key sequence composed of single-unit keying characters, said means including a cam-wheel mechanism for controlling said permutation bars; a set of contacts controlled by said stunt bars; and a distributor provided with segments which are in electrical connection with said contacts.

9. In a cryptograph, which employs a translator assembly having permutation bars and stunt bars in operative electrical connection; means for producing a relatively long cipher key sequence composed of single-unit keying characters, said means including a cam-wheel mechanism for controlling the permutation bars of said translator; a set of contacts controlled by.the stunt bars of said translator; a circuit including a switch board; and a distributor, the segments of which are connected to said contacts through said switchboard for reducing the number of effects obtainable from the translator to the number of segments on the distributor.

10. In a cryptograph which employs a translator assembly including permutation bars and stunt bars in operative circuit arrangement; means for producing a relatively long cipher key sequence, said means comprising a cam wheel mechanism for controlling said permutation bars; a set of contacts controlled by,said stunt bars; a switchboard; and a distributor having segments in electrical connection with said contacts through said switchboard adapted to reduce the number of eflects obtainable from said translator to the number of segments on the distributor, and to vary the connections between the driving said selected rotor or rotors sequentially and repetitively at a uniform angular velocity through all of their potential ciphering positions,

each complete revolution of said selected rotor or rotors constituting a ciphering cycle, and each said ciphering cycle corresponding to the time during which a key of the keyboard is depressed; and means for selecting one of said potential ciphering positions to become the operative ciphering position in said ciphering cycle.

12. In a cryptograph, a keyboard comprising a set or character elements; a corresponding set of signaling elements, both sets of elements being in operative electrical connection; a set of rotatable ciphering commutators for varying the connections between the character elements and the signalingelements, each tsaid commutators having a multiplicity ofpotential ciphering positions; means for selectively operating one or more of said commutators as rotors, including means for driving the same sequentially and repetitively at a uniform angular velocity through all of their potential ciphering positions, each complete revolution of said selected rotor or rotors constituting a ciphering cycle and each said ciphering cycle corresponding to the time during which a key of the keyboard is depressed; means for selecting one of said'pbtential ciphering positions to become the operative ciphering position in said ciphering cycle; and means for varving the selection of said potential ciphering position with successive ciphering cycles.

13. In a cryptograph, a keyboard comprising a set of character elements anda corresponding set of contacts electrically associated therewith; an indicating mechanism associated with the keyboard and comprising a set of signaling elements corresponding in number with the number of character elements of the keyboard; a circuit system including said sets of elements and a source of potential; means for automatically, rhythmically, and sequentially establishing a multiplicity of sets of different paths for the passage of electric currents from the contacts of the keyboard to the signaling elements of the indicating mechanism; means for momentarily selecting one of said sets of paths and simultaneously connecting the common terminal of the set of contacts of the keyboard to said source so that an electric current initiated by depressing one of the keys of the keyboard will flow along one of the paths in said selected set of paths to one of the signaling elements of the indicating mechanism; and means for varying said momentary selection of a set of said paths'with successive depressions of the keys of the keyboard.

14. In a cryptograph, a keyboard comprising a set of character elements and a corresponding set. of contacts electrically associated with the character elements; an indicating mechanism associated with said keyboard and comprising a corresponding set of signaling elements; multiple sets of electric conductors, and means for rhythmically and sequentially interposing said conductors between said keyboard and said indicating mechanism; means for selecting one of said sets of conductors and establishing operative electrical connections between the contacts of said keyboard and the signaling elements of said indicating mechanism; and means for varying said selection irregularly and with successive depressions of the keys of said keyboard.

15. In a cryptograph, a keyboard comprising character elements; a corresponding set of signaling elements in a potentially operative electrical connection with the keyboard; means comprising a rotatable commutator 'for varying the connections between the keyboard elements and the signaling elements; amotor to rotate the commutator at a constant speed, each complete revolution of the commutator comprising one operating cycle during which the keyboard may be operated in enciphering or deciphering; a cam-wheel mechanism comprising a set of cambearing rotatable members; means for angularly displacing the cam-bearing members upon operation of the keyboard; a set of contact levers and associated contacts controlled by the cam-wheel mechanism; a translator mechanism controlled by the cam-wheel mechanism for combining the efiects of the cam-controlled contacts and causing the selection of one of a plurality of cipherkeying circuits; a switchboard for reducingthe plurality of cipher-keying circuits to a number of circuits'corresponding with the number of character elements of the keyboard; a distributor comprising a plurality of insulated segments corresponding in number with the number of character elements of the keyboard and connected to one side of the switchboard; a brush arm carrying a brush 1 which sweeps over the segments of the distributor, the brush arm being keyed to the same shaft on which the commutator is rotated 50 that the commutator and the brush on the distributor face rotate synchronously; and a relay controlled by said distributor for connecting the keyboard to a power source for a specific instant in the operating cycle, said instant being determined by the cipher-key combination established by the cam-wheel mechanism.

16. In a cryptograph, a keyboard comprising a set of character elements with associated contacts; an indicating mechanism electrically associated with the keyboard and comprising a corresponding set of signaling elements; means for connecting the contacts with the signaling elements and for varying said connections sequentially and rhythmically in a multiplicity of ways, said means comprising stators and including ciphering rotors which are interposed between pairs of said stators and which have a multiplicity of potentially-operative ciphering positions with respect to said stators; a shaft carrying said rotors; means forrotating one or more of said rotors at a constant angular velocity; means for momentarily connecting the common terminal of the contacts of the keyboard in circuit relation when said selected rotors have reached a selected ciphering position, thus causing the selected ciphering position of the rotors to act as the operative ciphering position; and means for varying the selection of the driven rotors and of their operative ciphering positionwith successive depressions of the keys of the keyboard.

17. In a cryptograph including a keyboard comprising a set of character elements and a corresponding set of signaling elements; a circuit system including a source of potential: means for connecting the keyboard to said source for the purpose of establishing operative electrical connection between the keyboard and the signaling elements, said means being actuated only during a specific time-interval within a set of equal time-intervals into which each cycle of keyboard operation is divisible.

18. In a cryptograph including a keyboard comprising a set of character elements and a corresponding set of signaling elements; a circuit system including a source of potential; means for connecting the keyboard to said source for the purpose of establishing operative electrical connection between the keyboard and the signaling elements, said means being actuated only during a specific time-interval within a set of equal time-intervals into which each cycle of keyboard operation is divisible; and means for changing the successive actuating time-intervals. 

